West German Application No. 1,948,793, dated Sept. 26, 1969, discloses a method for preparation of a broad general class of 4,5,6,7-tetrahydroindazoles which are useful intermediates in the preparation of pharmaceuticals, agricultural chemicals and corrosion inhibitors. ##STR2##
Specifically disclosed is the preparation of Compound Ib, where R.sub.2, R.sub.3, and R.sub.4 are hydrogen and R.sub.1 is phenyl, from Compound IIb (same substitution) by catalytic reduction. The preparation and fungicidal utility of the 2-(4-chlorophenyl)-1,2,4,5,6,7-hexahydroindazol-3(3H)-one is disclosed in Takeda Chem. Ind. Paper, Chem. Abs., 67, 11542h (1967): ##STR3##
2-Aryl-4,5,6,7-tetrahydro-1-alkyl-1H-indazol-3(2H)-ones are claimed as antipyretics in Ger. 668,628 [assigned to P. Beierdorf & Co. AG, Chem. Abs., 33, 5131.sup.2 (1939)] and U.S. P. 2,104,348 [assigned to E. R. Squibb Co., Chem. Abs., 32, 1869.sup.1 (1938)]. ##STR4##
1-Phenyl-3,4-trimethylenepyrazolone is disclosed in U.S. Pat. No. 1,685,407 (1928) with utility as intermediate for making dyes and medicinal compounds. C. Mannich in Arch. Pharm. 267, 699-702 (1929) and in Brit. 260,577 describes the preparation of 1-phenyl-3,4-trimethylenepyrazolones. ##STR5##
R. P. Williams et al. in J. Med. Chem. 13, 773 (1970) reports the preparation and evaluation as anti-inflammatory agents compounds of the following type: ##STR6## X = H, Br, F.
Although some of the compounds disclosed in the above-cited references are useful as agricultural products, none are taught to be herbicides, especially selective herbicides. The presence of undesired vegetation is very damaging to useful crops such as rice and wheat. In the current world situation, wherein food shortages are acute, it is most important not to lose a portion of a valuable crop such as rice or wheat. The presence of such undesired vegetation results in the loss of a significant portion of such crops. Thus, a need exists for a particularly effective herbicide which will destroy as much unwanted vegetation as possible without causing significant damage to the desired crops, e.g. rice.
According to the instant invention, compounds have been discovered which are highly active herbicides and yet cause minimal damage to certain desired crops, e.g. rice and wheat.